The utility model provides an access control exhaust fan system of transformer substation, including the entrance guard of transformer substation device, visa card and SF6 device room fan, SF6 device room door -inhale device, a time relay and the 2nd time relay, the visa card is connected with the entrance guard of transformer substation device radio communication, first, the 2nd time relay is connected with the corresponding electricity with circulation ventilation control node of output control of withdrawing a garrison of the entrance guard of transformer substation device, the power end of SF6 device room door -inhale device is connected with the controlled electricity of output door -inhale control node of deploying troops on garrison duty of a time relay and the entrance guard of transformer substation device respectively, the power end of SF6 device room fan is connected with the controlled electricity of output fan control node of deploying troops on garrison duty of first, the 2nd time relay and the entrance guard of transformer substation device respectively. The utility model discloses thereby simple structure, lower, the easy realization of cost can effectively ensure staff's personal safety to SF6 electrical room forced draft when just using.